This invention relates to a control system for a hydraulic roof support assembly of an underground mining installation.
A known type of hydraulic roof support assembly is constituted by a plurality of identical roof support units positioned side-by-side along, for example, a longwall face. A known control system for such an assembly has a control valve assembly associated with each roof support unit. Each valve assembly consists of a set of similar pilot-operated (servo) control valves connected to a common hydraulic power supply line and to the rams operating that roof support unit. The control system is further provided with means for actuating the servo control valves from a remote point whereby automatic control of all units is achieved, and with means for effecting control of each unit from an adjacent roof support unit. In the latter case an operator can control a roof support unit while protected by the adjacent unit from which that control is being effected. This is known as proximity control.
In a known type of proximity control system, commands are emitted by an actuator on one roof support unit along a hydraulic control line to the control valve assembly of an adjacent roof support unit. The valves of this assembly are then pressurized by the hydraulic medium and actuate the associated hydraulic rams of that roof support unit. The actuator for controlling any given roof support unit is always mounted on the adjacent roof support unit up slope and in a position convenient for handling. The actuators are constituted by lever-actuated rotary slide valves.
A roof support control of this type is known in which the rotary slide valves (actuators) are each provided with an additional switching position, in which the sequence of mining operations comprising coal-cutting, advance and support setting of the roof support units is performed automatically without manual actuation of the actuators. In this case, the face workers may operate the roof support units either by manual adjustment of the actuators or cause the whole advance to be performed automatically. Manual or automatic operation may be switched on and off at any stage of the cycle. In this case, each of the control valves is provided with two separate control circuits for two servopistons mounted in parallel, one piston serving for manual control and the other for automatic control of the associated unit.
Another roof support control system is known having a manually actuated control valve and an automatic control valve actuated by remote signals. The two control valves are separated by a two-way valve so that the two control valves may be operated quite independently of one another. This type of roof support control system is suitable both for direct control of a roof support unit based on the principle of proximity control from an adjacent roof support unit as well as for performing automatically sequenced operation of the roof control units by remote control.
The aim of the invention is to provide a roof support control system of the proximity type which is relatively cheap and simple and in which, without basic changes to the roof support assembly, every roof support unit can be actuated selectively from either the righthand or lefthand adjacent roof support unit.